1. Field of the Invention
This invention relates to battery chargers and more particularly to an apparatus which causes the float voltage of one or more chargers to change so as to compensate for changes in battery ambient temperature.
2. DESCRIPTION OF PRIOR ART
Battery chargers, also known as rectifiers, are used by telephone operating companies to charge and maintain the charge on the batteries used by those companies. Once the battery is charged, the charge is maintained by the float voltage of the charger.
When batteries are exposed to wide variations in ambient temperature their life will be shortened unless the float voltage of the charger changes with the variation in ambient temperature. In other words, it is necessary to compensate for variations in ambient temperature by changing the float voltage so as to maximize battery life.
In the past this change in float voltage was accomplished either through a circuit internal to the charger which would provide the compensation based on the internal temperature of the charger or by a sensor extended outside of the charger. In either of the above arrangements each charger has its own compensation circuit. This may lead to problems where two or more chargers are connected to share the same load. With each charger having its own temperature compensation circuit, the chargers could drift apart which would be contrary to the desired load sharing.
It is desirable then to have a temperature compensation apparatus which can easily be included in chargers without redesigning the charger circuitry. It is further desirable that one temperature compensation apparatus be capable of controlling one or more chargers so that the chargers can, when they are connected to share a load, maintain that load sharing with changes in temperature. The apparatus of the present invention meets these requirements.